Coolant boiling over

[jwray76]

Just did a coolant flush recently. While I was at it I fixed the broken plastic elbow from the overflow tank. Also I went ahead and replaced the radiator cap. I put on a Stant car cap that had the right pressure rating and looked right (Advanced Auto didn't cary the exact model number listed in the x-reference thread). However I think it just isn't working properly.

Honestly the cap is one thing that I don't know if I truly understand how it should operate. Does it regulate the flow to the overflow by opening and closing at a certain pressure? I think the one I put on must have the wrong dimensions and therefore is letting the fluid flow to the overflow too early. I already ordered a new factory radiator cap, but just wondering if this is going to fix my problem.

By the way it seems like the fan is working properly and tstat is opening to circulate the coolant.

[John Stenhouse]

I seem to remember the Stant cap being no good, it appears to fit but doesn't do the job properly. No idea if that will fix your problem, but it may go some way to it with a factory cap on.

[walker]

the difference I could see between the stant and the OEM cap was that the outer tabs on the cap, which lock the cap in place - they are a bit taller on the stant. Almost one millimeter. This means that when it's tightened down, there is the possibility that it won't have as much preload pressure on the spring.... so it could be boiling over early.

I was able to bend the tabs on the stant, but ended up just getting the triumph cap.

[D-Fuzz]

When you say the coolant is boiling over, do you mean it is getting pushed out of the expansion tank?  If so, I had a similar thing with mine, thought it was a bad sign, but it turned out to be air in the system from changing the coolant and it just needed to be burped out.  As the engine gets hot, the air expands and pushes the coolant out.  It stopped after a few good burps/rides.

[jwray76]

When you say the coolant is boiling over, do you mean it is getting pushed out of the expansion tank?  If so, I had a similar thing with mine, thought it was a bad sign, but it turned out to be air in the system from changing the coolant and it just needed to be burped out.  As the engine gets hot, the air expands and pushes the coolant out.  It stopped after a few good burps/rides.

''

yes it is getting pushed out of the expansion tank. Have riddnen enough now though that I am pretty sure it isn't air. I think that the rad cap just isn't building pressure like it should be.

Can someone confirm that the rad cap does open/close to control flow to the expansion tank?

[Mustang]

well of course it does .......water can't get to the resivoir until the pressure rating of the cap is achieved and the cap opens

[jwray76]

well of course it does .......water can't get to the resivoir until the pressure rating of the cap is achieved and the cap opens

OK, thanks for confirming. I am pretty sure this is my problem then. I think that the cap never properly seals the small tube to the reservoir. Therefore even before the pressure is reached the coolant is boiling over to the tank.

[daveb]

I had a similar problem a few weeks back, OEM rad cap from dealer sorted out the problem.

see link http://tigertriple.com/forum/index.php/topic,8892

[prbarr]

I had the same problem with a Stant cap.  If you look at it side by side with the stock cap, you'll see that the Stant cap is slightly shorter than the stock cap.  It doesn't extend far enough into the radiator, so it doesn't seal properly.  Once the coolant heats up, it goes straight into the overflow.  I went back to a stock cap and the problem was solved.

I posted something on this awhile back with a picture.  Can't locate it now though...

[jwray76]

Thanks guys, pretty certain that this is my problem. I have the factory cap in and some new metal fuel fittings. So when I get a chance next weekend I am gonna pull it back down again. At least I needed to do the fuel fittings anyways.

Gonna ride it a bit tomorrow to use up that gas in the tank. Shouldn't be too hot so I should be fine. Just gotta keep it movin!

[Mustang]

I had the same problem with a Stant cap.  If you look at it side by side with the stock cap, you'll see that the Stant cap is slightly shorter than the stock cap.  It doesn't extend far enough into the radiator, so it doesn't seal properly.  Once the coolant heats up, it goes straight into the overflow.  I went back to a stock cap and the problem was solved.

I posted something on this awhile back with a picture.  Can't locate it now though...

http://tigertriple.com/forum/viewtopic. ... 7056#47056